Access to abstract permanently restricted to Ball State community only / Access to thesis permanently restricted to Ball State community only / Department of Chemistry

This thesis comprises three chapters united by a single theme: development of alkali metal cation sensors based on ion complexing macrocycles. In part 1, benzo-18-crown-6 and cryptand 2.2.2B were immobilised on polyacrylic acid backbone through an amide linkage. The benzo-18-crown-6 and 2.2.2B were functionalised using the Friedal-Crafts acylation reaction with ω-amino acids. The spacer between the polymer backbone and the crown ether was varied by using co-amino acids with varying numbers of methylene groups [special characters omitted]. Attempts to use co-amino acids with an intermediate spacer length [special characters omitted] failed due to formation of a cyclic imine. The amino crown ethers were immobilised on a poly(acryloyl chloride). Polymers 2a, 5ad and 6a failed to give self supporting membranes but a polymer blend with PVC/Plasticizer was employed for membrane fabrication. Ion Selective Electrodes (ISEs) and Coated Wire Electrodes (CWEs) were made from polymer blend membranes and their response to alkali metal cations was tested. The ISEs made with mobile carriers were active, while those prepared from immobilised carriers were inactive. The reverse was the case with CWEs. This dichotomy existed in all cases. The selectivity of the ionophores among the alkali metals was unaffected by linkage to the polymer backbone. However, the alkali metal/alkaline earth metal selectivity was enhanced. The effect of plasticizer and hydrophilic additives on electrode response was insignificant. The spacer length had considerable influence: the longer the spacer, the better the electrode response of the CWEs. In part 2, the mass transport of ions across the polymer blend membrane under a temperature gradient was investigated. The immobilised polymers prepared in part 1 were used here to fabricate membranes from polymer blends with NOMEX. In thermodialysis experiments, a low level of ion transport was detected. These preliminary experiments led to a rediscovery of membrane distillation. The scope of this latter process with hydrophobic membranes was explored in detail. Part 3 was devoted to the design and synthesis of water soluble photoionophores. Three series of molecules were synthesised: captands, bis crown ether compounds and phenol derivatives of tartaro crown ether carboxylic adds. Captand molecules were synthesised by a capping reaction of crown ether tetraacid chloride 14 with 1,3-bis(aminomwthyl) benzene, 1,4- bis(aminomethyl) benzene and 2,2’-bis(aminomethyl) biphenyl. Crystals of meta- and para xylene capped molecules were grown and their structures solved to establish the conformation of the molecules. Fluorescence quenching studies of these molecules were done in 0.3% methanol:water (v/v). Quenching due to alkali metal ions was insignificant ( < 20%) while copper and mercury cations quenched the emission significantly ( > 90%). Stern-Volmer analysis showed an upward curvature indicating association between the ligand and the cations [special characters omitted] cations, but dynamic and static components of the quenching could not be separated. Potentiometric titration with a potassium selective electrodes was carried out to obtain the stability constants for these ligands with potassium ion. The bis crown ethers 28 and 29, designed to increase water solubility, were prepared by the reaction of anhydride 27 with 9,10-bis(ammomethyl) anthracene and 1,2-bis(aminomethyl) benzene. The pKa values of the ligands and their stability constants with alkali and alkaline earth metal ions were determined by potentiometric titration. Fluorescence quenching studies were done in aqueous buffer at pH 10. These compounds also failed to give an emission quenching in the presence of alkali or alkaline earth metal cations, but both copper and mercury cations showed a significant amount of quenching. Stability constants were derived from emission quenching studies for [special characters omitted]. Chromoionophores, phenol derivatives of tartaro crown ethers, were synthesised from the reaction of crown ether anhydrides and 2-aminophenol. The structure of the compound 31 was assigned as the syn isomer based on nmr data in comparison to literature reports. Absorption studies were carried out in water. The absorption spectra of compound 30 were perturbed by alkali metal as well as alkaline earth metal ions, while the absorption spectrum of compound 31 showed no response to varying cation concentration. The lack of response from compound 31 was attributed to the competitive binding of cations among syn carboxylic groups away from the syn phenolic groups. / Graduate

Three cage-functionalized polyoxacrown ethers (9, 10 and 12) and four novel cage-functionalized polyoxamonoazacrown ethers (18, 20, 25 and 29) that contain 3,5-disubstituted-4-oxahexacyclo[5.4.0.02,6.03,10.05,9.08,11]dodecane ("oxahexacyclic") moiety have been synthesized and their respective alkali metal picrate extraction profiles along with that of three analogues 13, 14 and 21 have been obtained. The observed avidities and selectivities of the host molecules toward complexation and transport of alkali metal picrates can be related to the size and shape of their respective macrocyclic cavity and the number of donor atoms. The effect of N-alkyl substitution on the complexation properties of azacrown ethers has been studied. The avidity of N-Et azacrown ethers toward complexation with alkali metal cations is generally higher than that of the corresponding non-N-alkylated hosts. However, the presence of an N-Et group appears to have a negligible effect upon their relative selectivities in their regards. The effect of pH on extraction process was studied; it was thereby determined that the alkali metal picrate extraction experiments are best performed at high pH (ca. 11-12).

Yes / The creation of ternary multi-component crystals through the introduction of 18-crown-6 to direct the hydrogen-bonding motifs of the other molecular components was investigated for 3,5-dinitrobenzoic acid (3,5-dnba) with 4-aminobenzoic acid (4-aba). The creation of a binary complex between 18-crown-6 and 4-aba (C12H24O6·2C7H7NO2)2 and a ternary salt between 3,5-dnba, 18-crown-6 and 4-aba (C12H24O6·C7H8NO2+·C7H3N2O6−·C7H4N2O6) were confirmed by single-crystal structure determination. In both structures, the amino molecules bind to the crown ether through N—H...O hydrogen bonds, leaving available only a single O atom site on the crown with restricted geometry to potentially accept a hydrogen bond from 3,5-dnba. While 3,5-dnba and 4-aba form a binary co-crystal containing neutral molecules, the shape-selective nature of 18-crown-6 preferentially binds protonated amino molecules, thereby leading to the formation of the ternary salt, despite the predicted low concentration of the protonated species in the crystallizing solution. Thus, through the choice of crown ether it may be possible to control both location and nature of the available bonding sites for the designed creation of ternary crystals.

Three different types of cage crown ethers have been prepared and their complexation properties with Ag(I) have been studied. Atomic absorption, fluorescence quenching, and UV absorption have been used to study the interaction between the hosts (cage crown ethers) and guests (Ag+). For the cage-annulated crown ethers that contain aromatic rings, cation-π and π-π interactions may contribute significantly to the overall complexation ability of the host system. Piperazine groups may cooperate, and the piperazine nitrogen atoms provide unshared electrons, which may form a complex with Ag+. In addition, relatively soft donor atoms (e.g., Br) are well-suited for complexation with Ag+, which is a softer Lewis acid than alkali metal cations.

Quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been synthesized as possible specific metal host systems. The synthesis and characterization of quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been described. The characterization of these host systems have been fully achieved in solution by using various techniques such as IR, 1H NMR, and 13C NMR spectroscopic methods, high-resolution mass spectrometry (HRMS), elemental microanalysis, and X-ray crystallographic analysis in case of one quinoxaline-functionalized, cage-annulated oxacrown ether compound. The synthesis of the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) is described. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligand bmi proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(bmi) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)N(tolyl-p)C(O)]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(bmi) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(bmi), whose molecular structure has been determined by X-ray crystallography. The kinetics for the ligand isomerization have been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-348 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Orthometalation of one of the phenyl groups associated with the bmi ligand is triggered by near-UV photolysis of the chelating cluster 1,1- Os3(CO)10(bmi).

Thesis (M.S.)--Rochester Institute of Technology, 2004. / Typescript. Includes bibliographical references (leaves 121-123).

Thesis (M. Sc.)--Carleton University, 1993. / Also available in electronic format on the Internet.

D.Phil. (Chemistry) / The problem of maintaining good quality of water for domestic use and for aquatic life remains a challenge. Water sources are often contaminated with pollutants from natural sources such as volcanic eruptions and by human activities such as manufacturing industries, mining, water-purification processes, agricultural activities and a vast number of other activities. Water-purification processes used by municipal authorities are designed to remove most of the pollutants but some trace amounts will always remain and have been detected in drinking water and treated waste water reservoirs. These trace amounts pose a threat to human health and the well-being of aquatic life. The detection of these trace amounts of pollutants is often carried out by laboratory-based techniques that require sophisticated, expensive instruments and often require extensive sample preparation and pre-concentration. Simple, quick and in-field detection methods are necessary especially for remote small communities with limited or no access to laboratories. Optical detection systems offer hope as a solution to this problem. In this work newly developed fluorescence-based molecular sensors for the detection of pollutants in water were developed, characterised and tested for their sensing abilities towards organic and inorganic pollutants. The fluorescent probes for organic pollutants were designed based on the host-guest chemistry of the cyclodextrin molecule. Azo dye-modified β-cyclodextrins were synthesised and linked via ethylene glycol and epichlorohydrin to produce the sensors that were then tested for their sensing response towards chlorophenols and small aliphatic chlorinated alkanes which are often formed during the disinfection of water in the purification process. The sensor molecules were characterised by UV-Vis, FT-IR and 1D and 2D NMR spectroscopy. The amount of cyclodextrin in each sensor molecule was quantified using the anthrone method (67%) as well as by 1H-NMR spectroscopy (72%). To demonstrate the host-guest interaction of the sensor molecules, isothermal titration calorimetry (ITC) was used. ITC measurements showed that modifying β-cyclodextrin and using linkers did not alter its host-guest interaction with guest molecules as demonstrated by the stoichiometry, n, stability (or binding or association) constant (K) and thermodynamic parameters of the interaction. The sensor molecule linked via ethylene glycol showed selectivity towards 4- chlorophenol among the chlorophenols investigated and has the potential to be used in a sensor for the detection of 4-chlorophenol. The sensor molecule linked via epichlorohydrin showed sensitivity towards chloroform, a typical disinfection by-product. These experimental results showed that the sensor molecules could be used for quick on-field detection of chlorinated organic compounds in water. Sensor molecules for inorganic pollutants were based on the complex formation of crown ethers with metal ions. The sensor was formed by modifying a dibenzo-18- crown-6 ether molecule with an azo dye. The sensor was then characterised using UV-Vis spectrophotmetry, FT-IR and NMR spectroscopies as well as mass spectrometry and CHNS elemental analysis. The sensor molecule was then subjected to different metal ions and the fluorescence change of the probe observed. Interestingly, the sensor was highly sensitive and selective to mercury (II) and Cu (II) ions in water. Mercury (II) is one of the most hazardous heavy metals among the heavy-metal ions found in environmental waters and its early detection in water sources is important. The synthesised molecular sensor can therefore be incorporated into a simple hand-held gadget with a light source and be used for on-field detection of mercury (II) ions in remote areas.

Novel cage-functionalized azacrown ethers, i.e. 51, 52, 53, 55, 57, 61 and 62, which have various crown cavity and different number of nitrogen atoms incorporated, have been prepared. X-ray structures of 53, 55 and 57 have been obtained for the study of the crown topological structure. The complexation properties of crown 51, 52, 57, 61 and 62 have been evaluated via alkali metal picrate extraction, silver picrate extraction and ESI-MS study. The novel cage-fuctionalized azacrown ethers generally exhibit high avidity and selectivity towards Ag+ versus alkali metal ions and some transition metals i.e. Cu2+, Mn2+, Zn2+, Ni2+ and Pb2+. Crown 61 displays significant avidity and selectivity toward K+ in alkali metal picrate extraction experiments vis-à-vis the remaining alkali metal picrates. Three types of ditopic ion-exchange receptors for sodium hydroxide extraction study have been designed. All of the crown ether molecules have proper cavity for selective sodium complexation and have weakly acidic ionizable alcohols for sodium-proton exchange under strongly basic conditions. Crown 80 and 81 were synthesized; key intermediates for the synthesis of crown 82, 83 and 84 have been prepared. The preparation of 99 afforded an unexpected crown 103. The preparation of 109 had been attempted, but could not be successfully isolated. Four novel cage-functionalized calix[4]arene crown-5, i.e. 113-116, have been synthesized. The structures of 113 and 116 have been established by X-ray crystal structural analysis and NMR spectral analysis. The complexation properties of the four ionic receptors have been studied via alkali metal picrate extraction experiments. Crown 115 and 116 display more than modest avidity toward alkali metal ions and are most selective toward K+ vis-à-vis 113 and 114.